P.I. versus carbs?

[mleadbeater]

Although I haven’t given up trying to sort my ‘6 ‘s PI syste, on which the main issue is the tendency to bog on acceleration , Ive had thoughts about converting to carbs. Can you please comment on the following question.

If converting to carbs, probably SUs or Strombergs, roughly how much power loss will this produce? and change in economy?

What are  the pros/cons of these carbs?

Is my car, a mid 73 model fitted with the long port head? how do I tell the difference?

Webers are another option, and comments on these?, are used ones ok?

Finally , any experience with converting to electronic PI?

I don’t want to spend a lot on my car, just want it to be a pleasure to drive, not too worried about driving quickly.

Cheers

Mike 

 

[Mk2 Chopper]

https://www.tr-register.co.uk/forums/index.php?/topic/85619-fuel-injection-swap-to-carbs-a-conundrum/

[harlequin]

My 72 TR6 has a CP engine so 9..5:1 compression ratio and CP cam running on Strombergs with an electric fuel pump.

It returns high 20s around local roads and 30 plus on a run. On a  local rolling road it produced 135bhp. It drives really pleasantly with loads of torque and will comfortably trickel along at 30mph in top and then pick up smoothly. At one point I had SUs but couldn't get them to run as well as the Strombergs.

I often drive in the company of a TR5 and a CP injected 6 without getting left behind, and I certainly appreciate the simplicity, reliability and economy of my setup.

Having said that a TR6 is expected to be PI so if you intend selling the car sort the PI out, or if your plan is for the kids to eventually sell it give it a try.

George 

[roy53]

3.8 jaguars run happily on 3 SU so a 2.5 should be happy on 2 SU. The 2500 saloons were ok as well.

Roy

[harlequin]

21 minutes ago, roy53 said:

3.8 jaguars run happily on 3 SU so a 2.5 should be happy on 2 SU. The 2500 saloons were ok as well.

Roy

I agree  Roy there is  nothing wrong with SUs, I have them on my TR3 and it runs great, but the 6 was only OKish, whereas with the Strombergs it is smoother, has better economy and instant starting.

I have no idea why it should be so, maybe its because the Strombergs are concentric or its a quirk of my car?

George 

[roy53]

That goes to show that 2 carbs are OK. May be just the tune on your SUs.

 

[harlequin]

41 minutes ago, roy53 said:

That goes to show that 2 carbs are OK. May be just the tune on your SUs.

 

Yes maybe it's the carbs, I did buy them new from Burlin but I suppose its possible that one of them is not quite 100%

George 

[iani]

2 hours ago, roy53 said:

3.8 jaguars run happily on 3 SU so a 2.5 should be happy on 2 SU. The 2500 saloons were ok as well.

Roy

US market 4.2l Jaguars were happy on 2 SU's, the triples overfuelled but they just look so very good.

[DRD]

14 hours ago, harlequin said:

Yes maybe it's the carbs, I did buy them new from Burlin but I suppose its possible that one of them is not quite 100%

George 

What needles were you using and were they setup properly?

[harlequin]

1 hour ago, DRD said:

What needles were you using and were they setup properly?

It was some years ago that I gave up on the SUs so I'm a bit vague on the details but I think BDM were tried along with others, the car was put on two different rolling roads and as I said it ran OK but not great. So in a bit of lateral thinking I tried the Strombergs that came with the car, I disabled the temperature compensator and bypass valve to simplify things and put in new spindel seals and it has now run as it should for the last six or seven years.

George 

 

[stuart]

17 hours ago, iani said:

US market 4.2l Jaguars were happy on 2 SU's, the triples overfuelled but they just look so very good.

Actually it was UK market ones (apart from the short lived 420 model) and they were HD8 not HS6, US market XJ6 had Strombergs for emission reasons. However all world 3.8 models had HS6 and were capable of 230hp.

Stuart.

[john.r.davies]

Mike,
It would be a shame to replace your Pi!   Do you have a copy of the Manual:  http://www.tr6pi.com/Lucas Petrol Injection.pdf   It used to be available as a reprint from the Wheatsheaf Press, Wilmslow, SK9 4BQ, but I bought mine long ago.   They are on Facebook at https://www.facebook.com/wheatsheafprint/?locale=en_GB

And do you know one of the several PI specialists, who may be able to recalibrate your Metering Unit?    I used to use Malcolm at Prestige;  he has now retired and his business taken on by Carl at TR Traders, who I've found to be reliable.

John
PS You have a PM, on a different matter.

Edited December 10, 2023 by john.r.davies

[Rob Salisbury]

Back in the early '70s the Police ran both 2.5Pi and 2500S saloons as squad cars, my brother had a police friend who drove both and said you could always tell when you were driving a Pi, though they eventually kept a pack of Cardice round the pump, would have made much more sense to have mounted the pump on the other side of the boot away from the rear exhaust box.

[iani]

3 hours ago, stuart said:

Actually it was UK market ones (apart from the short lived 420 model) and they were HD8 not HS6, US market XJ6 had Strombergs for emission reasons. However all world 3.8 models had HS6 and were capable of 230hp.

Stuart.

 

Edited December 10, 2023 by iani

[Tim D.]

I recently had a very original 2500TC running twin sus.  Really sweetly running car and pretty quick. Have run PI on the TR6 and worked well apart from the slightly clunky start and rich at idle that are part of PI ownership. But loved the clockwork nature of the system. Very ingenious. Now run a twin barrel holley on the supercharger setup. Also works well once setup properly. Took a years work to get their. Also ran twin DHLAs on an elan I had. Again fair amount of time setting them up.  I guess this is a long winded way of saying all systems can be made to run well and reliably. I like the challenge if doing this (e.g.AFR logger).

Tim

[CharlieBubbles]

22 hours ago, john.r.davies said:

Mike,
It would be a shame to replace your Pi!   Do you have a copy of the Manual:  http://www.tr6pi.com/Lucas Petrol Injection.pdf   It used to be available as a reprint from the Wheatsheaf Press, Wilmslow, SK9 4BQ, but I bought mine long ago.   They are on Facebook at https://www.facebook.com/wheatsheafprint/?locale=en_GB

And do you know one of the several PI specialists, who may be able to recalibrate your Metering Unit?    I used to use Malcolm at Prestige;  he has now retired and his business taken on by Carl at TR Traders, who I've found to be reliable.

John
PS You have a PM, on a different matter.

+1 for Carl Fitchett; great guy, great service